Calipers have been created in different configurations for different purposes. They have their use in a vast array of fields from architectural and engineering drafting to furniture making and measuring. They are used in machine-shop work and for measuring navigational maps and the like. The present method for measuring or setting a caliper is to lay it on a ruler and read the opening of the caliper against the ruler markings. This approach is very inaccurate, inconsistent and thus open to errors. A previously known device for setting outside calipers is called a “turning tree,” which is a solid of revolution which has a plurality of decreasing cylinders of known diameters. Such a device is accurate when properly used, but it is difficult to assure that the caliper gauge tips are precisely set on the exact diameter. There is need for a gauge by which a caliper can be set accurately and accurately read.